The invention relates to a method for shortening the flap of a paper roll for on-the-fly roll replacement and to an apparatus for carrying out this method.
Continuously operating paper processing machines, especially roll-rotating machines, have paper webs which are wound off of rolls. When one roll reaches its end, it is replaced by a new roll without bringing the processing machine to standstill. Roll changers are known which operate by a so-called unsupported roll change or roll change on-the-fly principle. Thus at the beginning of a roll change a new roll in a standby position is initially provided with a glued tip. The new roll is then set into rotation and brought to a peripheral speed which is synchronized with the speed of the web running from the practically empty roll. The web is pressed at the correct point in time against the new roll so that it contacts the new roll in the region of the glued tip. Thus the beginning of the new web is glued onto the traveling web. The traveling web is cut shortly behind the glue location.
In accordance with DE 26 19 236 C3, in which a roll changer with an associated control is described, the so-called xe2x80x9cglue flapxe2x80x9d segment of the old web has a predetermined length from the glue location to the separated end to enable the glue flap to travel through the printing machine without detriment.
It has been found, however, that this flap in subsequent processing stations can be the source of detriment when it has its usual length. Since the cut always is delayed partially by the inertial mass of the separating device and as a function of the cycling time of the controller, the flap cannot be made optionally short at the outset. If there is, for example, a delay of say 10 ms and the web speed is 15 m/s, the flap is at least 150 mm long.
According to DE 29 11 268 A1, which describes a similar roll changer, utilizing a nonstop deflection of the material web, the flap is held as short as possible since it can be detrimental for further processing. This is achieved according to the mentioned publication in that on the new roll behind the glueable region a tear strand serving as a separating element is stretched which extends at an inclination above the material web and is provided with an entrainer. This remains adherent upon the pressing of the paper web against the new roll to the pressing roll and activates the tear strand so that it will separate the paper web. It is thus possible to glue the runoff paper web without a flap onto the new paper web.
It has been found in practice, however, that the cost of roll preparation and the control of the tear strand after gluing are comparatively expensive. As a result this process has not been widely used in practice.
In the method which has become known from DE 20 23 100 B2 and the associated apparatus, the new web is initially fed parallel to the running-off web with a slight distance therefrom in a connecting stretch and is accelerated to its velocity. Then one of the two webs is pressed onto an adhesive strip glued on both sides and then pressed with the adhesive strip against the other web. The trailing end of the runoff web is cut off with a blade disposed at the start of the connecting stretch. The segment of the runoff web which is located between the adhesive location and the cutting location is the flap. At the end of the connecting stretch, a second blade is arranged at a short spacing from the surface of a deflecting roller and has its cutting edge oriented counter to the travel direction of the paper web. This blade serves to separate the leading end of the new web. This blade is not suitable for shortening the flap since the latter is disposed on the inner side of the arc as the webs pass around the deflecting roller so that this flap is clamped between the web and the surface of the deflecting roller.
It is an object of the invention to provide a method whereby the flap can be foreshortened to an undetrimental degree before it travels into a subsequent processing station.
It is also an object to provide an apparatus which is appropriate for carrying out the new method.
These objects are attained in a method for shortening a flap hanging from a paper web in conjunction with a roll replacement on the fly in which a continuous paper web is withdrawn from a roll coming to an end is withdrawn and fed to a processing station and the beginning of a new roll provided with glue and synchronized with the continuous paper web is pressed thereagainst and then after a brief time interval the original web is lopped. According to the invention, the paper web glued together and from which the flap still hangs is guided along a straight segment of its path, on the side on which the web is found, an air stream traveling in the same direction as the web travel is generated which spreads over the paper web at least over a part of the straight path segment while the flap travels this part, and the flap erected by the air stream is cut off at the latest when it reaches the end of the straight path segment.
An apparatus for shortening the flap hanging from a glued-together paper web in conjunction with a roll replacement on the fly can include an unwinding unit equipped with a device for roll replacement on the fly, in which a continuous paper web which is withdrawn from a roll reaching its end and fed to a processor is pressed against the beginning of a new roll synchronized with the continuous paper web and provided with glue. Then after a brief interval the original web is lopped. Two deflecting rolls can be provided between which the paper web travels in a straight path segment and
a cutting tool can be provided in the region of the straight path segment at a short distance from the paper web and with a cutting edge oriented opposite the web travel direction.
A blowing nozzle can be disposed approximately at the start of the straight path segment adjacent the paper web.
The blowing nozzle as seen in the web travel direction, can be disposed upstream of the inlet side deflecting roller.
A baffle plate can be disposed approximately parallel to the paper web along the straight path segment.
A suction box with a collecting sieve can be arranged adjacent the cutting tool. The collecting sleeve can be an endlessly traveling collection sieve.
A blower can be provided with a suction side connected with the suction box and a pressure side connected with the blowing nozzle.
A blower element can be provided for the passing paper web neighboring the cutting tool.
A support element for the web can be swingable selectively into a standby position or into an active position.